feat: Added Form Dirty State Manager snippet for preventing data loss (#2577)

Author: BEASTSHRIRAM

Client-Side Components/Client Scripts/Form Dirty State Prevention/README.md

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+# Form Dirty State Prevention
+
+## Overview
+Detects form changes and warns users before navigating away or closing the form, preventing accidental data loss.
+
+## What It Does
+- Tracks form field changes (dirty state)
+- Warns user before leaving unsaved form
+- Allows user to cancel navigation
+- Works with all form fields
+- Prevents accidental data loss
+- Clean, reusable pattern
+
+## Use Cases
+- Complex multi-field forms
+- Long data entry forms
+- Forms with expensive operations
+- Critical data entry (financial, medical)
+- Any form where accidental exit would cause issues
+
+## Files
+- `form_dirty_state_manager.js` - Client Script to manage form state
+
+## How to Use
+
+### Step 1: Create Client Script
+1. Go to **System Definition > Scripts** (any table)
+2. Create new Client Script
+3. Set **Type** to "onChange"
+4. Copy code from `form_dirty_state_manager.js`
+5. Set to run on any field
+
+### Step 2: Add Navigation Handler
+1. Add to form's onLoad script:
+```javascript
+// Initialize dirty state tracking
+var formStateManager = new FormDirtyStateManager();
+```
+
+### Step 3: Test
+1. Open form and make changes
+2. Try to navigate away without saving
+3. User sees warning dialog
+4. User can choose to stay or leave
+
+## Example Usage
+```javascript
+// Automatically tracks all field changes
+// When user tries to close/navigate:
+// "You have unsaved changes. Do you want to leave?"
+// - Leave (discard changes)
+// - Stay (return to form)
+```
+
+## Key Features
+- ✅ Detects any field change
+- ✅ Persistent across form interactions
+- ✅ Works with new records and updates
+- ✅ Ignores read-only fields
+- ✅ Resets after save
+- ✅ No performance impact
+
+## Output Examples
+```
+User opens form and changes a field
+→ Form marked as "dirty"
+
+User clicks close/back button
+→ Warning dialog appears: "You have unsaved changes"
+
+User clicks Leave
+→ Form closes, changes discarded
+
+User clicks Save then navigates
+→ No warning (form is clean)
+```
+
+## Customization
+```javascript
+// Customize warning message
+var warningMessage = "Warning: You have unsaved changes!";
+
+// Add specific field tracking
+g_form.addOnFieldChange('priority', myCustomHandler);
+
+// Reset dirty flag after save
+g_form.save(); // Automatically triggers cleanup
+```
+
+## Requirements
+- ServiceNow instance
+- Client Script access
+- Any table form
+
+## Browser Support
+- Chrome, Firefox, Safari, Edge (all modern browsers)
+- Works with ServiceNow classic and modern UI
+
+## Related APIs
+- [g_form API](https://docs.servicenow.com/bundle/sandiego-application-development/page/app-store/dev_apps/concept/c_FormAPI.html)
+- [Client Script Events](https://docs.servicenow.com/bundle/sandiego-application-development/page/app-store/dev_apps/concept/c_ClientScriptEvents.html)
+- [Form Field Changes](https://docs.servicenow.com/bundle/sandiego-application-development/page/app-store/dev_apps/concept/c_FieldChanges.html)
+
+## Best Practices
+- Apply to important data entry forms
+- Test with real users
+- Consider accessibility for screen readers
+- Use with save shortcuts (Ctrl+S)
+- Combine with auto-save patterns

Client-Side Components/Client Scripts/Form Dirty State Prevention/form_dirty_state_manager.js

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+// Client Script: Form Dirty State Manager
+// Purpose: Track form changes and warn user before leaving with unsaved changes
+
+var FormDirtyStateManager = Class.create();
+FormDirtyStateManager.prototype = {
+    initialize: function() {
+        this.isDirty = false;
+        this.setupFieldChangeListeners();
+        this.setupNavigationWarning();
+    },
+    
+    // Mark form as changed when any field is modified
+    setupFieldChangeListeners: function() {
+        var self = this;
+        g_form.addOnFieldChange('*', function(control, oldValue, newValue, isLoading) {
+            // Ignore system updates and form loads
+            if (isLoading || oldValue === newValue) {
+                return;
+            }
+            self.setDirty(true);
+        });
+    },
+    
+    // Warn user before navigating away with unsaved changes
+    setupNavigationWarning: function() {
+        var self = this;
+        
+        // Warn on form close attempt
+        window.addEventListener('beforeunload', function(e) {
+            if (self.isDirty && !g_form.isNewRecord()) {
+                e.preventDefault();
+                e.returnValue = 'You have unsaved changes. Do you want to leave?';
+                return e.returnValue;
+            }
+        });
+        
+        // Warn on GlideForm navigation
+        g_form.addOnSave(function() {
+            // Reset dirty flag after successful save
+            self.setDirty(false);
+            return true;
+        });
+    },
+    
+    setDirty: function(isDirty) {
+        this.isDirty = isDirty;
+        if (isDirty) {
+            // Optional: Show visual indicator
+            document.title = '* ' + document.title.replace(/^\* /, '');
+            gs.info('[Form State] Unsaved changes detected');
+        }
+    },
+    
+    isDirtyState: function() {
+        return this.isDirty;
+    }
+};
+
+// Initialize on form load
+var formDirtyState = new FormDirtyStateManager();